Bearing Bits

**pds0006** · 11-10-2005, 02:29 PM

Can you put a bearing on a standard bit and make it a pattern cutting bit? For example, put a 1/2" O.D. bearing on a 1/2" straight bit and effectively have a template routing bit? Am I right, or is there something I've missed? Thank in advance for the info!

**arcticfox46** · 11-10-2005, 04:02 PM

YES you CAN do that.

Speaking as an engineer working in a machining industry I can honestly say YES.

HeHeHeHe - BUT - It will cost about 10-20 times more that a brand new Freud, or heck even a Whiteside would cost.

The precision involved with aligning the bearing precisly with the 2 cutting edges would make it cost prohibitive - not impossible, just very expensive.

Maybe there is an easier way that I have no clue about, - totally possible, - but the way I would go about it, would definately NOT be worth it.

My recomenndation - Go buy a pattern bit for $25 or $40.

**TDHofstetter** · 11-10-2005, 10:37 PM

I do have one pattern bit with a removable bearing. That bearing has a 1/4" bore and a locking device (with an Allen screw), so it could be moved around from bit to bit... and I HAVE moved it to one or two other straight bits for that purpose.

I don't like doing that very much, though, because most bits don't have a very long shank... and when that bearing (with locking device) is installed, there's not much shank left to be gripped by the chuck.

The pattern bit was built with an unusually long shank, and so leaves me plenty to hang onto.

You could theoretically do the same with an "ordinary" bearing with the correct ID and OD... but you'd have to be sure that the bearing was built and rated for a good 25,000 RPM. It'd have to be either shielded or sealed, and either way lubricated with a true high-speed lubricant that won't simply fling out as the bearing spins up & down. The OD would have to be a size that's just right for your application, unless you were willing to modify your template accordingly. If the bearing's smaller than the OD of the bit (say in the case of an ogee or roundover bit), you stand a chance of biting a hole out of your template at either the start or the end of the cut.

It CAN be done, though.

If you use a free bearing (without any locking device), temporarily attach it to the bit's shank with some sort of stickum that'll clean off easily & completely. If you want to "permanentize" it, stick it there with LockTite (which can be released later, if you MUST, by appying heat - but that MAY ruin the bit or the bearing, so don't make it any practice).

-- Tim --

The more I know
The more I learn,
And the more I learn
The more I know
I have yet to learn.
Don't wait up,
I'll be a while.

**pds0006** · 11-11-2005, 07:35 AM

Sounds like my best bet is just to get the pattern cutting bit. I'll be "smart" for once. Thanks for the info guys!

**arcticfox46** · 11-12-2005, 04:59 PM

That sounds a little different than what I was thinking. I was thinking of taking a straight cutting bit and turning it into a flush cutting bit.

A pattern bit has the bearing on the shank end of the bit. Little different scenerio there. Still, Tim, on a pattern bit with the bearing on the shank end isn't the OD of the bearing the same size as the cutter OD. Maybe a 1/4 shank bit with a 1/2 OD could work. But like you said, that doesn't leave much to grip in a collet.

**TDHofstetter** · 11-12-2005, 07:00 PM

Ah - you were thinking TOP bearing instead of BOTTOM bearing.

YOWTCH - making a TOP-bearing follower would be a real bugger. That'd take a metal lathe with a toolpost grinder.

Yeah, usually a bottom-bearing pattern bit does have a bearing the same OD (within a couple of thousandths, anyway) as the bit.

I do have one largish top-bearing bit (a rabbeting bit) with a slew of different-sized bearings, and a couple of ogee & roundover bits with both 1/2" and 5/8" bearing to accomodate reveal / no reveal.

-- Tim --

The more I know
The more I learn,
And the more I learn
The more I know
I have yet to learn.
Don't wait up,
I'll be a while.